TPA4860 1-W MONO AUDIO POWER AMPLIFIER SLOS164A – SEPTEMBER 1996 – REVISED MARCH 2000 D D D D D D D D D D 1-W BTL Output (5 V, 0.2 % THD+N) 3.3-V and 5-V Operation No Output Coupling Capacitors Required Shutdown Control (IDD = 0.6 µA) Headphone Interface Logic Uncompensated Gains of 2 to 20 (BTL Mode) Surface-Mount Packaging Thermal and Short-Circuit Protection High Power Supply Rejection (56-dB at 1 kHz) LM4860 Drop-In Compatible D PACKAGE (TOP VIEW) GND SHUTDOWN HP-SENSE GND BYPASS HP-IN1 HP-IN2 GND 1 16 2 15 3 14 4 13 5 12 6 11 7 10 8 9 GND VO 2 IN+ IN– VDD GAIN VO 1 GND description The TPA4860 is a bridge-tied load (BTL) audio power amplifier capable of delivering 1 W of continuous average power into an 8-Ω load at 0.4 % THD+N from a 5-V power supply in voiceband frequencies (f < 5 kHz). A BTL configuration eliminates the need for external coupling capacitors on the output in most applications. Gain is externally configured by means of two resistors and does not require compensation for settings of 2 to 20. Features of this amplifier are a shutdown function for power-sensitive applications as well as headphone interface logic that mutes the output when the speaker drive is not required. Internal thermal and short-circuit protection increases device reliability. It also includes headphone interface logic circuitry to facilitate headphone applications. The amplifier is available in a 16-pin SOIC surface-mount package that reduces board space and facilitates automated assembly. typical application circuit VDD 12 VDD/2 RF Audio Input RI 11 GAIN 13 IN – 14 IN + VDD CS VO1 10 CI 1W CB VDD NC Headphone Plug 5 BYPASS 6 HP-IN1 7 HP-IN2 3 HP-SENSE 2 SHUTDOWN VO2 15 RPU Bias Control 1, 4, 8, 9, 16 Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet. Copyright 2000, Texas Instruments Incorporated PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters. POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 1 TPA4860 1-W MONO AUDIO POWER AMPLIFIER SLOS164A – SEPTEMBER 1996 – REVISED MARCH 2000 AVAILABLE OPTIONS PACKAGED DEVICE TA SMALL OUTLINE (D) – 40°C to 85°C TPA4860D absolute maximum ratings over operating free-air temperature range (unless otherwise noted)† Supply voltage, VDD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 V Input voltage, VI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –0.3 V to VDD +0.3 V Continuous total power dissipation . . . . . . . . . . . . . . . . . . . . . internally limited (See Dissipation Rating Table) Operating free-air temperature range, TA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –40°C to 85°C Storage temperature range, Tstg . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –65°C to 150°C Lead temperature 1,6 mm (1/16 inch) from case for 10 seconds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260°C † Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated under “recommended operating conditions” is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability. DISSIPATION RATING TABLE PACKAGE D TA ≤ 25°C 1250 mW DERATING FACTOR 10 mW/°C TA = 70°C 800 mW TA = 85°C 650 mW recommended operating conditions ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ Supply voltage, VDD Common mode input voltage, Common-mode voltage VIC VDD = 3.3 V VDD = 5 V Operating free-air temperature, TA 2 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 MIN MAX 2.7 5.5 UNIT V 1.25 2.7 V 1.25 4.5 V –40 85 °C TPA4860 1-W MONO AUDIO POWER AMPLIFIER SLOS164A – SEPTEMBER 1996 – REVISED MARCH 2000 electrical characteristics at specified free-air temperature range, VDD = 3.3 V (unless otherwise noted) TPA4860 ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁ Á ÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ Á ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁ Á ÁÁÁ ÁÁ Á ÁÁÁ ÁÁ ÁÁÁ Á ÁÁÁ ÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ PARAMETER VOO TEST CONDITIONS Output offset voltage (measured differentially) See Note 1 Supply ripple rejection ratio VDD = 3.2 V to 3.4 V MIN TYP MAX 5 20 UNIT mV 75 dB IDD Quiescent current 2.5 mA IDD(M) IDD(SD) Quiescent current, mute mode 750 µA Quiescent current, shutdown mode 0.6 µA VIH VIL High-level input voltage (HP-IN) 1.7 V Low-level input voltage (HP-IN) 1.7 V VOH VOL High-level output voltage (HP-SENSE) IO = 100 µA IO = –100 µA Low-level output voltage (HP-SENSE) 2.5 2.8 0.2 V 0.8 V NOTE 1: At 3 V < VDD < 5 V the dc output voltage is approximately VDD/2. operating characteristics, VDD = 3.3 V, TA = 25°C, RL = 8 Ω ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁ Á ÁÁ Á ÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁÁÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁÁÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ PARAMETER PO BOM B1 power see Note 2 Output power, Maximum output power bandwidth Unity-gain bandwidth Supply ripple rejection ratio Vn TEST CONDITIONS THD = 0.2%, AV = 2 f = 1 kHz, THD = 2%, AV = 2 f = 1 kHz, Gain = 10, THD = 2% TPA4860 MIN TYP MAX UNIT 350 mW 500 mW 20 kHz Open Loop 1.5 MHz BTL f = 1 kHz 56 dB SE f = 1 kHz 30 dB Gain = 2 20 µV Noise output voltage, see Note 3 NOTES: 2. Output power is measured at the output terminals of the device. 3. Noise voltage is measured in a bandwidth of 20 Hz to 20 kHz. POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 3 TPA4860 1-W MONO AUDIO POWER AMPLIFIER SLOS164A – SEPTEMBER 1996 – REVISED MARCH 2000 electrical characteristics at specified free-air temperature range, VDD = 5 V (unless otherwise noted) TPA4860 ÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁ Á ÁÁÁ ÁÁ Á ÁÁÁ ÁÁ ÁÁÁ Á ÁÁÁ ÁÁ ÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ PARAMETER VOO TEST CONDITIONS Output offset voltage See Note 1 Supply ripple rejection ratio VDD = 4.9 V to 5.1 V MIN TYP MAX 5 20 UNIT mV 70 dB IDD Supply current 3.5 mA IDD(M) IDD(SD) Supply current, mute 750 µA Supply current, shutdown 0.6 µA VIH VIL High-level input voltage (HP-IN) 2.5 V Low-level input voltage (HP-IN) 2.5 V VOH VOL High-level output voltage (HP-SENSE) IO = 500 µA IO = – 500 µA Low-level output voltage (HP-SENSE) 2.5 2.8 0.2 V 0.8 V NOTE 1: At 3 V < VDD < 5 V the dc output voltage is approximately VDD/2. operating characteristic, VDD = 5 V, TA = 25°C, RL = 8 Ω ÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁ Á ÁÁ Á ÁÁ ÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁÁÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁÁÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ PARAMETER PO BOM B1 power see Note 2 Output power, Maximum output power bandwidth Unity-gain bandwidth Supply ripple rejection ratio Vn TEST CONDITIONS THD = 0.2%, AV = 2 f = 1 kHz, THD = 2%, AV = 2 f = 1 kHz, Gain = 10, THD = 2% TYP MAX UNIT 1000 mW 1100 mW 20 kHz Open Loop 1.5 MHz BTL f = 1 kHz 56 dB SE f = 1 kHz 30 dB Gain = 2 20 µV Noise output voltage, see Note 3 NOTES: 2. Output power is measured at the output terminals of the device. 3. Noise voltage is measured in a bandwidth of 20 Hz to 20 kHz. 4 TPA4860 MIN POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 TPA4860 1-W MONO AUDIO POWER AMPLIFIER SLOS164A – SEPTEMBER 1996 – REVISED MARCH 2000 TYPICAL CHARACTERISTICS ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁ ÁÁÁÁ ÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁ ÁÁÁÁ Table of Graphs FIGURE VOO IDD THD+N IDD Vn Output offset voltage Distribution 1,2 Supply current distribution vs Free-air temperature 3,4 vs Frequency 5,6,7,8,9, 10,11,15, 16,17,18 vs Output power 12,13,14, 19,20,21 Supply current vs Supply voltage 22 Output noise voltage vs Frequency Maximum package power dissipation vs Free-air temperature Power dissipation vs Output power Maximum output power vs Free-air temperature 28 vs Load Resistance 29 vs Supply Voltage 30 Total harmonic distortion plus noise Output power 23,24 25 26,27 Open loop frequency response vs Frequency 31 Supply ripple rejection ratio vs Frequency 32,33 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 5 TPA4860 1-W MONO AUDIO POWER AMPLIFIER SLOS164A – SEPTEMBER 1996 – REVISED MARCH 2000 TYPICAL CHARACTERISTICS DISTRIBUTION OF TPA4860 OUTPUT OFFSET VOLTAGE DISTRIBUTION OF TPA4860 OUTPUT OFFSET VOLTAGE 25 25 VCC = 5 V VCC = 3.3 V 20 Number of Amplifiers Number of Amplifiers 20 15 10 5 15 10 5 0 –3 –2 –1 0 1 2 3 4 5 6 0 7 –3 –2 VOO – Output Offset Voltage – mV –1 0 1 2 5 6 Figure 2 SUPPLY CURRENT DISTRIBUTION vs FREE-AIR TEMPERATURE SUPPLY CURRENT DISTRIBUTION vs FREE-AIR TEMPERATURE 3.5 4.5 VCC = 5 V VCC = 3.3 V 4 3 3.5 I DD – Supply Current – mA I DD – Supply Current – mA 4 VOO – Output Offset Voltage – mV Figure 1 3 2.5 Typical 2 1.5 1 2.5 2 Typical 1.5 1 0.5 0.5 0 0 –20 25 85 –20 TA – Free-Air Temperature – °C 25 Figure 4 POST OFFICE BOX 655303 85 TA – Free-Air Temperature – °C Figure 3 6 3 • DALLAS, TEXAS 75265 7 TPA4860 1-W MONO AUDIO POWER AMPLIFIER SLOS164A – SEPTEMBER 1996 – REVISED MARCH 2000 TYPICAL CHARACTERISTICS 10 VDD = 5 V PO = 1 W AV = –2 V/V RL = 8 Ω 1 CB = 0.1 µF 0.1 CB = 1 µF 0.01 20 TOTAL HARMONIC DISTORTION PLUS NOISE vs FREQUENCY THD+N – Total Harmonic Distortion Plus Noise – % THD+N – Total Harmonic Distortion Plus Noise – % TOTAL HARMONIC DISTORTION PLUS NOISE vs FREQUENCY 100 1k 10 k 20 k 10 VDD = 5 V PO = 1 W AV = –10 V/V RL = 8 Ω 1 0.1 0.01 20 CB = 0.1 µF CB = 1 µF 100 f – Frequency – Hz Figure 5 VDD = 5 V PO = 1 W AV = –20 V/V RL = 8 Ω 1 CB = 1 µF 0.1 100 1k 10 k 20 k TOTAL HARMONIC DISTORTION PLUS NOISE vs FREQUENCY THD+N – Total Harmonic Distortion Plus Noise – % THD+N – Total Harmonic Distortion Plus Noise – % 10 0.01 20 10 k 20 k Figure 6 TOTAL HARMONIC DISTORTION PLUS NOISE vs FREQUENCY CB = 0.1 µF 1k f – Frequency – Hz 10 VDD = 5 V PO = 0.5 W AV = –2 V/V RL = 8 Ω 1 CB = 0.1 µF 0.1 CB = 1 µF 0.01 20 f – Frequency – Hz 100 1k 10 k 20 k f – Frequency – Hz Figure 7 Figure 8 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 7 TPA4860 1-W MONO AUDIO POWER AMPLIFIER SLOS164A – SEPTEMBER 1996 – REVISED MARCH 2000 TYPICAL CHARACTERISTICS 10 VDD = 5 V PO = 0.5 W AV = –10 V/V RL = 8 Ω CB = 0.1 µF 1 0.1 CB = 1 µF 0.01 20 100 1k TOTAL HARMONIC DISTORTION PLUS NOISE vs FREQUENCY THD+N – Total Harmonic Distortion Plus Noise – % THD+N – Total Harmonic Distortion Plus Noise – % TOTAL HARMONIC DISTORTION PLUS NOISE vs FREQUENCY 10 k 20 k 10 CB = 0.1 µF 1 CB = 1 µF 0.1 0.01 20 100 f – Frequency – Hz VDD = 5 V AV = –10 V/V Single Ended RL = 8 Ω PO = 250 mW RL = 32 Ω PO = 60 mW 100 TOTAL HARMONIC DISTORTION PLUS NOISE vs OUTPUT POWER THD+N – Total Harmonic Distortion Plus Noise – % THD+N – Total Harmonic Distortion Plus Noise – % 10 0.01 20 1k 10 k 20 k 10 VDD = 5 V AV = –2 V/V RL = 8 Ω f = 20 Hz 1 CB = 0.1 µF CB = 1 µF 0.1 0.01 0.02 f – Frequency – Hz 0.1 PO – Output Power – W Figure 11 8 10 k 20 k Figure 10 TOTAL HARMONIC DISTORTION PLUS NOISE vs FREQUENCY 0.1 1k f – Frequency – Hz Figure 9 1 VDD = 5 V PO = 0.5 W AV = –20 V/V RL = 8 Ω Figure 12 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 1 2 TPA4860 1-W MONO AUDIO POWER AMPLIFIER SLOS164A – SEPTEMBER 1996 – REVISED MARCH 2000 TYPICAL CHARACTERISTICS 10 VDD = 5 V AV = –2 V/V RL = 8 Ω f = 1 kHz 1 CB = 0.1 µF 0.1 0.01 0.02 TOTAL HARMONIC DISTORTION PLUS NOISE vs OUTPUT POWER THD+N – Total Harmonic Distortion Plus Noise – % THD+N – Total Harmonic Distortion Plus Noise – % TOTAL HARMONIC DISTORTION PLUS NOISE vs OUTPUT POWER 0.1 1 2 10 VDD = 5 V AV = –2 V/V RL = 8 Ω f = 20 kHz CB = 0.1 µF 1 0.1 0.01 0.02 0.1 PO – Output Power – W Figure 13 TOTAL HARMONIC DISTORTION PLUS NOISE vs FREQUENCY THD+N – Total Harmonic Distortion Plus Noise – % THD+N – Total Harmonic Distortion Plus Noise – % 10 VDD = 3.3 V PO = 350 mW RL = 8 Ω AV = –2 V/V 1 CB = 0.1 µF 0.1 CB = 1 µF 100 1k 2 Figure 14 TOTAL HARMONIC DISTORTION PLUS NOISE vs FREQUENCY 0.01 20 1 PO – Output Power – W 10 k 20 k 10 VDD = 3.3 V PO = 350 mW RL = 8 Ω AV = –10 V/V 1 CB = 0.1 µF 0.1 CB = 1 µF 0.01 20 100 1k 10 k 20 k f – Frequency – Hz f – Frequency – Hz Figure 16 Figure 15 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 9 TPA4860 1-W MONO AUDIO POWER AMPLIFIER SLOS164A – SEPTEMBER 1996 – REVISED MARCH 2000 TYPICAL CHARACTERISTICS TOTAL HARMONIC DISTORTION PLUS NOISE vs FREQUENCY 10 THD+N – Total Harmonic Distortion Plus Noise – % THD+N – Total Harmonic Distortion Plus Noise – % TOTAL HARMONIC DISTORTION PLUS NOISE vs FREQUENCY VDD = 3.3 V PO = 350 mW RL = 8 Ω AV = –20 V/V CB = 0.1 µF 1 CB = 1 µF 0.1 0.01 20 100 1k 10 k 20 k 10 VDD = 3.3 V AV = –10 V/V Single Ended 1 RL = 8 Ω PO = 250 mW 0.01 20 Figure 17 Figure 18 CB = 0.1 µF CB = 1.0 µF 0.1 1 2 10 VDD = 3.3 V AV = –2 V/V RL = 8 Ω f = 1 kHz 1 CB = 0.1 µF 0.1 0.01 0.02 0.1 PO – Output Power – W PO – Output Power – W Figure 19 10 Figure 20 POST OFFICE BOX 655303 10 k 20 k TOTAL HARMONIC DISTORTION PLUS NOISE vs OUTPUT POWER THD+N – Total Harmonic Distortion Plus Noise – % THD+N – Total Harmonic Distortion Plus Noise – % VDD = 3.3 V AV = –2 V/V RL = 8 Ω f = 20 Hz 0.01 0.02 1k f – Frequency – Hz 10 0.1 100 f – Frequency – Hz TOTAL HARMONIC DISTORTION PLUS NOISE vs OUTPUT POWER 1 RL = 32 Ω PO = 60 mW 0.1 • DALLAS, TEXAS 75265 1 2 TPA4860 1-W MONO AUDIO POWER AMPLIFIER SLOS164A – SEPTEMBER 1996 – REVISED MARCH 2000 TYPICAL CHARACTERISTICS SUPPLY CURRENT vs SUPPLY VOLTAGE 10 5 TA = 0°C TA = –20°C 4 1 I DD – Supplu Current – mA THD+N – Total Harmonic Distortion Plus Noise – % TOTAL HARMONIC DISTORTION PLUS NOISE vs OUTPUT POWER CB = 0.1 µF 0.1 VDD = 3.3 V AV = –2 V/V RL = 8 Ω f = 20 kHz 0.01 20 m 0.1 1 TA = 25°C 3 2 1 0 2.5 2 TA = 85°C 3 PO – Output Power – W 3.5 Figure 21 5 5.5 OUTPUT NOISE VOLTAGE vs FREQUENCY 103 103 VCC = 3.3 V 102 V01 +V02 V02 101 V01 100 1k 10 k 20 k Vn – Output Noise Voltage – µ V VCC = 5 V Vn – Output Noise Voltage – µ V 4.5 Figure 22 OUTPUT NOISE VOLTAGE vs FREQUENCY 1 20 4 VDD – Supply Voltage – V 102 V01 +V02 V02 101 V01 1 20 100 1k 10 k 20 k f – Frequency – Hz f – Frequency – Hz Figure 23 Figure 24 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 11 TPA4860 1-W MONO AUDIO POWER AMPLIFIER SLOS164A – SEPTEMBER 1996 – REVISED MARCH 2000 TYPICAL CHARACTERISTICS MAXIMUM PACKAGE POWER DISSIPATION vs FREE-AIR TEMPERATURE POWER DISSIPATION vs OUTPUT POWER 1.5 VDD = 5 V 1.25 RL = 4 Ω Power Dissipation – W Maximum Package Power Dissipation – W 1.5 1 0.75 0.5 1 RL = 8 Ω 0.5 0.25 RL = 16 Ω 0 –25 0 0 25 50 75 100 125 150 175 0 0.25 TA – Free-Air Temperature – °C 0.5 0.75 1 1.25 1.5 1.75 PO – Output Power – W Figure 25 Figure 26 POWER DISSIPATION vs OUTPUT POWER MAXIMUM OUTPUT POWER vs FREE-AIR TEMPERATURE 1 160 VDD = 3.3 V TA – Free-Air Temperature – °C Power Dissipation – W 140 0.75 RL = 4 Ω 0.5 RL = 8 Ω 0.25 RL = 16 Ω 120 100 80 RL = 8 Ω 60 40 RL = 4 Ω 20 RL = 16 Ω 0 0 0 0.25 0.5 0.75 0 0.25 PO – Output Power – W Figure 27 12 0.5 0.75 Figure 28 POST OFFICE BOX 655303 1 1.25 PO – Maximum Output Power – W • DALLAS, TEXAS 75265 1.50 TPA4860 1-W MONO AUDIO POWER AMPLIFIER SLOS164A – SEPTEMBER 1996 – REVISED MARCH 2000 TYPICAL CHARACTERISTICS OUTPUT POWER vs LOAD RESISTANCE OUTPUT POWER vs SUPPLY VOLTAGE 1.4 2 AV = –2 V/V f = 1 kHz CB = 0.1 µF THD+n ≤ 1% 1.75 1 PO – Power Output – W PO – Power Output – W 1.2 0.8 0.6 VCC = 5 V 0.4 0.2 AV = –2 V/V f = 1 kHz CB = 0.1 µF THD+n ≤ 1% 1.5 1.25 RL = 4 Ω 1 RL = 8 Ω 0.75 0.5 RL = 16 Ω 0.25 VCC = 3.3 V 0 4 8 12 16 20 24 28 32 36 40 44 0 2.5 48 3.5 3 Load Resistance – Ω Figure 29 5.5 0 0° –45° 60 Phase –90° 40 Gain –135° –180° 0 Supply Ripple Rejection Ratio – dB 45° VDD = 5 V RL = 8 Ω CB = 0.1 µF Phase G – Gain – dB 5 SUPPLY RIPPLE REJECTION RATIO vs FREQUENCY OPEN LOOP FREQUENCY RESPONSE 20 4.5 Figure 30 100 80 4 Supply Voltage – V –10 –20 VDD = 5 V RL = 8 Ω Bridge Tied Load –30 –40 CB = 0.1 µF –50 –60 CB = 1 µF –70 –80 –90 –20 10 100 1k 10 k 100 k 1M –225° 10 M –100 100 1k 10 k 20 k f – Frequency – Hz f – Frequency – Hz Figure 31 Figure 32 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 13 TPA4860 1-W MONO AUDIO POWER AMPLIFIER SLOS164A – SEPTEMBER 1996 – REVISED MARCH 2000 TYPICAL CHARACTERISTICS SUPPLY RIPPLE REJECTION RATIO vs FREQUENCY Supply Ripple Rejection Ratio – dB 0 –10 –20 CB = 0.1 µF VDD = 5 V RL = 8 Ω Single Ended –30 –40 –50 –60 CB = 1 µF –70 –80 –90 –100 100 1k 10 k 20 k f – Frequency – Hz Figure 33 APPLICATION INFORMATION bridged-tied load versus single-ended mode Figure 34 shows a linear audio power amplifier (APA) in a bridge tied load (BTL) configuration. A BTL amplifier actually consists of two linear amplifiers driving both ends of the load. There are several potential benefits to this differential drive configuration but initially let us consider power to the load. The differential drive to the speaker means that as one side is slewing up the other side is slewing down and vice versa. This in effect doubles the voltage swing on the load as compared to a ground referenced load. Plugging twice the voltage into the power equation, where voltage is squared, yields 4 times the output power from the same supply rail and load impedance (see equation 1). V (rms) + 2O(PP) Ǹ2 Power + V 14 V (rms) 2 (1) RL POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 TPA4860 1-W MONO AUDIO POWER AMPLIFIER SLOS164A – SEPTEMBER 1996 – REVISED MARCH 2000 APPLICATION INFORMATION bridged-tied load versus single-ended mode (continued) VDD VO(PP) 2x VO(PP) RL VDD –VO(PP) Figure 34. Bridge-Tied Load Configuration In a typical computer sound channel operating at 5 V, bridging raises the power into a 8-Ω speaker from a singled-ended (SE) limit of 250 mW to 1 W. In sound power, that is a 6-dB improvement which is loudness that can be heard. In addition to increased power there are frequency response concerns, consider the single-supply SE configuration shown in Figure 35. A coupling capacitor is required to block the dc offset voltage from reaching the load. These capacitors can be quite large (approximately 40 µF to 1000 µF) so they tend to be expensive, occupy valuable PCB area, and have the additional drawback of limiting low-frequency performance of the system. This frequency limiting effect is due to the high pass filter network created with the speaker impedance and the coupling capacitance and is calculated with equation 2. fc + 2 p R1 C (2) L C For example, a 68-µF capacitor with an 8-Ω speaker would attenuate low frequencies below 293 Hz. The BTL configuration cancels the dc offsets, which eliminates the need for the blocking capacitors. Low-frequency performance is then limited only by the input network and speaker response. Cost and PCB space are also minimized by eliminating the bulky coupling capacitor. VDD VO(PP) CC RL VO(PP) Figure 35. Single-Ended Configuration POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 15 TPA4860 1-W MONO AUDIO POWER AMPLIFIER SLOS164A – SEPTEMBER 1996 – REVISED MARCH 2000 APPLICATION INFORMATION bridged-tied load versus single-ended mode (continued) Increasing power to the load does carry a penalty of increased internal power dissipation. The increased dissipation is understandable considering that the BTL configuration produces 4 times the output power of the SE configuration. Internal dissipation versus output power is discussed further in the thermal considerations section. BTL amplifier efficiency Linear amplifiers are notoriously inefficient. The primary cause of these inefficiencies is voltage drop across the output stage transistors. There are two components of the internal voltage drop. One is the headroom or dc voltage drop that varies inversely to output power. The second component is due to the sinewave nature of the output. The total voltage drop can be calculated by subtracting the RMS value of the output voltage from VDD. The internal voltage drop multiplied by the RMS value of the supply current, IDDrms, determines the internal power dissipation of the amplifier. An easy to use equation to calculate efficiency starts out as being equal to the ratio of power from the power supply to the power delivered to the load. To accurately calculate the RMS values of power in the load and in the amplifier, the current and voltage waveform shapes must first be understood (see Figure 36). IDD VO IDD(RMS) V(LRMS) Figure 36. Voltage and Current Waveforms for BTL Amplifiers Although the voltages and currents for SE and BTL are sinusoidal in the load, currents from the supply are very different between SE and BTL configurations. In an SE application the current waveform is a half-wave rectified shape, whereas in BTL it is a full-wave rectified waveform. This means RMS conversion factors are different. Keep in mind that for most of the waveform both the push and pull transistor are not on at the same time, which supports the fact that each amplifier in the BTL device only draws current from the supply for half the waveform. The following equations are the basis for calculating amplifier efficiency. 16 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 TPA4860 1-W MONO AUDIO POWER AMPLIFIER SLOS164A – SEPTEMBER 1996 – REVISED MARCH 2000 APPLICATION INFORMATION Efficiency + PP L (3) SUP Where: V Lrms PL + VǸ2P + V Lrms 2 RL 2 + 2R Vp L + VDD IDDrms + VDDp R2VP L 2V P I DDrms + pR P SUP L Efficiency of a BTL Configuration p VP + 2V DD + p ǒ Ǔ P LR L 2 ń 1 2 (4) 2V DD NO TAG employs equation 4 to calculate efficiencies for four different output power levels. Note that the efficiency of the amplifier is quite low for lower power levels and rises sharply as power to the load is increased, resulting in a nearly flat internal power dissipation over the normal operating range. Note that the internal dissipation at full output power is less than in the half power range. Calculating the efficiency for a specific system is the key to proper power supply design. For a stereo 1-W audio system with 8-Ω loads and a 5-V supply, the maximum draw on the power supply is almost 3.25 W. Table 1. Efficiency vs Output Power in 5-V 8-Ω BTL Systems OUTPUT POWER (W) EFFICIENCY (%) PEAK-TO-PEAK VOLTAGE (V) INTERNAL DISSIPATION (W) 0.25 31.4 2.00 0.55 0.50 44.4 2.83 0.62 1.00 62.8 4.00 4.47† 0.59 1.25 70.2 † High peak voltages cause the THD to increase. 0.53 A final point to remember about linear amplifiers whether they are SE or BTL configured is how to manipulate the terms in the efficiency equation to utmost advantage when possible. Note that in equation 4, VDD is in the denominator. This indicates that as VDD goes down, efficiency goes up. For example, if the 5-V supply is replaced with a 10-V supply (TPA4860 has a maximum recommended VDD of 5.5 V) in the calculations of NO TAG then efficiency at 1 W would fall to 31% and internal power dissipation would rise to 2.18 W from 0.59 W at 5 V. Then for a stereo 1-W system from a 10-V supply, the maximum draw would be almost 6.5 W. Choose the correct supply voltage and speaker impedance for the application. POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 17 TPA4860 1-W MONO AUDIO POWER AMPLIFIER SLOS164A – SEPTEMBER 1996 – REVISED MARCH 2000 APPLICATION INFORMATION selection of components Figure 37 is a schematic diagram of a typical notebook computer application circuit. 50 kΩ CF 50 kΩ VDD 12 CS VDD/2 RF Audio Input RI 11 GAIN 13 IN – 14 IN + VDD = 5 V VO1 10 CI 46 kΩ CB 1W Internal Speaker 46 kΩ 5 BYPASS 6 HP-IN1 7 HP-IN2 3 HP-SENSE 2 SHUTDOWN VO2 15 VDD RPU NC Bias Control 1, 4, 8, 9, 16 Headphone Plug Figure 37. TPA4860 Typical Notebook Computer Application Circuit gain setting resistors, RF and RI ǒǓ The gain for the TPA4860 is set by resistors RF and RI according to equation 5. Gain + *2 RF (5) RI BTL mode operation brings about the factor of 2 in the gain equation due to the inverting amplifier mirroring the voltage swing across the load. Given that the TPA4860 is a MOS amplifier, the input impedance is very high, consequently input leakage currents are not generally a concern although noise in the circuit increases as the value of RF increases. In addition, a certain range of RF values is required for proper startup operation of the amplifier. Taken together it is recommended that the effective impedance seen by the inverting node of the amplifier be set between 5 kΩ and 20 kΩ. The effective impedance is calculated in equation 6. Effective Impedance + RRF)RRI F (6) I As an example, consider an input resistance of 10 kΩ and a feedback resistor of 50 kΩ. The gain of the amplifier would be –10 and the effective impedance at the inverting terminal would be 8.3 kΩ, which is well within the recommended range. 18 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 TPA4860 1-W MONO AUDIO POWER AMPLIFIER SLOS164A – SEPTEMBER 1996 – REVISED MARCH 2000 APPLICATION INFORMATION gain setting resistors, RF and RI (continued) For high performance applications metal film resistors are recommended because they tend to have lower noise levels than carbon resistors. For values of RF above 50 kΩ the amplifier tends to become unstable due to a pole formed from RF and the inherent input capacitance of the MOS input structure. For this reason, a small compensation capacitor of approximately 5 pF should be placed in parallel with RF. This, in effect, creates a low pass filter network with the cutoff frequency defined in equation 7. f c(lowpass) + 2 p R1 C (7) F F For example, if RF is 100 kΩ and Cf is 5 pF then fc is 318 kHz, which is well outside of the audio range. input capacitor, CI In the typical application an input capacitor, CI, is required to allow the amplifier to bias the input signal to the proper dc level for optimum operation. In this case, CI and RI form a high-pass filter with the corner frequency determined in equation 8. + 2 p R1 C f c(highpass) (8) I I The value of CI is important to consider as it directly affects the bass (low frequency) performance of the circuit. Consider the example where RI is 10 kΩ and the specification calls for a flat bass response down to 40 Hz. Equation 8 is reconfigured as equation 9. CI + 2 p 1R fc (9) I In this example, CI is 0.40 µF, so one would likely choose a value in the range of 0.47 µF to 1 µF. A further consideration for this capacitor is the leakage path from the input source through the input network (RI, CI) and the feedback resistor (RF) to the load. This leakage current creates a dc offset voltage at the input to the amplifier that reduces useful headroom, especially in high gain applications. For this reason a low-leakage tantalum or ceramic capacitor is the best choice. When polarized capacitors are used, the positive side of the capacitor should face the amplifier input in most applications as the dc level there is held at VDD/2, which is likely higher that the source dc level. Note that it is important to confirm the capacitor polarity in the application. power supply decoupling, CS The TPA4860 is a high-performance CMOS audio amplifier that requires adequate power supply decoupling to ensure the output total harmonic distortion (THD) is as low as possible. Power supply decoupling also prevents oscillations for long lead lengths between the amplifier and the speaker. The optimum decoupling is achieved by using two capacitors of different types that target different types of noise on the power supply leads. For higher frequency transients, spikes, or digital hash on the line, a good low equivalent-series-resistance (ESR) ceramic capacitor, typically 0.1 µF placed as close as possible to the device VDD lead, works best. For filtering lower-frequency noise signals, a larger aluminum electrolytic capacitor of 10 µF or greater placed near the power amplifier is recommended. POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 19 TPA4860 1-W MONO AUDIO POWER AMPLIFIER SLOS164A – SEPTEMBER 1996 – REVISED MARCH 2000 APPLICATION INFORMATION midrail bypass capacitor, CB The midrail bypass capacitor, CB, serves several important functions. During start-up or recovery from shutdown mode, CB determines the rate at which the amplifier starts up. This helps to push the start-up pop noise into the subaudible range (so low it can not be heard). The second function is to reduce noise produced by the power supply caused by coupling into the output drive signal. This noise is from the midrail generation circuit internal to the amplifier. The capacitor is fed from a 25-kΩ source inside the amplifier. To keep the start-up pop as low as possible, the relationship shown in equation 10 should be maintained. ǒ CB 1 25 kΩ Ǔvǒ Ǔ 1 CI RI (10) As an example, consider a circuit where CB is 0.1 µF, CI is 0.22 µF and RI is 10 kΩ. Inserting these values into the equation 9 we get: 400 ≤ 454 which satisfies the rule. Bypass capacitor, CB, values of 0.1 µF to 1 µF ceramic or tantalum low-ESR capacitors are recommended for the best THD and noise performance. single-ended operation Figure 38 is a schematic diagram of the recommended SE configuration. In SE mode configurations, the load should be driven from the primary amplifier output (OUT1, terminal 10). VDD 12 CS VDD/2 RF Audio Input RI 11 GAIN 13 IN – VDD = 5 V VO1 10 CC 250-mW External Speaker CI 14 IN + CB 5 VO2 15 BYPASS RSE = 50 Ω CSE = 0.1 µF Figure 38. Singled-Ended Mode ǒǓ Gain is set by the RF and RI resistors and is shown in equation 11. Since the inverting amplifier is not used to mirror the voltage swing on the load, the factor of 2 is not included. Gain +* RF (11) RI The phase margin of the inverting amplifier into an open circuit is not adequate to ensure stability, so a termination load should be connected to VO2. This consists of a 50-Ω resistor in series with a 0.1-µF capacitor to ground. It is important to avoid oscillation of the inverting output to minimize noise and power dissipation. 20 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 TPA4860 1-W MONO AUDIO POWER AMPLIFIER SLOS164A – SEPTEMBER 1996 – REVISED MARCH 2000 APPLICATION INFORMATION single-ended operation (continued) The output coupling capacitor required in single-supply SE mode also places additional constraints on the selection of other components in the amplifier circuit. The rules described earlier still hold with the addition of the following relationship: ǒ CB 1 25 kΩ Ǔvǒ ǓƠ 1 CI RI 1 R LC C (12) output coupling capacitor, CC In the typical single-supply SE configuration, an output coupling capacitor (CC) is required to block the dc bias at the output of the amplifier thus preventing dc currents in the load. As with the input coupling capacitor, the output coupling capacitor and impedance of the load form a high-pass filter governed by equation 13. f c high + 2 p R1 C (13) L C The main disadvantage, from a performance standpoint, is that the load impedances are typically small, which drives the low-frequency corner higher. Large values of CC are required to pass low frequencies into the load. Consider the example where a CC of 68 µF is chosen and loads vary from 8 Ω, 32 Ω, to 47 kΩ. Table 2 summarizes the frequency response characteristics of each configuration. Table 2. Common Load Impedances vs Low Frequency Output Characteristics in SE Mode RL 8Ω CC 68 µF LOWEST FREQUENCY 32 Ω 68 µF 73 Hz 47,000 Ω 68 µF 0.05 Hz 293 Hz As Table 2 indicates, most of the bass response is attenuated into 8-Ω loads while headphone response is adequate and drive into line level inputs (a home stereo for example) is very good. headphone sense circuitry, Rpu The TPA4860 is commonly used in systems where there is an internal speaker and a jack for driving external loads (i.e., headphones). In these applications, it is usually desirable to mute the internal speaker(s) when the external load is in use. The headphone inputs (HP-1, HP-2) and headphone output (HP-SENSE) of the TPA4860 were specifically designed for this purpose. Many standard headphone jacks are available with an internal single-pole single-throw (SPST) switch that makes or breaks a circuit when the headphone plug is inserted. Asserting either or both HP-1 and/or HP-2 high mutes the output stage of the amplifier and causes HP-SENSE to go high. In battery-powered applications where power conservation is critical HP-SENSE can be connected to the shutdown input as shown in Figure 39. This places the amplifier in a very low current state for maximum power savings. Pullup resistors in the range from 1 kΩ to 10 kΩ are recommended for 5-V and 3.3-V operation. POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 21 TPA4860 1-W MONO AUDIO POWER AMPLIFIER SLOS164A – SEPTEMBER 1996 – REVISED MARCH 2000 APPLICATION INFORMATION VDD RPU NC Headphone Plug 6 HP-IN1 7 HP-IN2 3 HP-SENSE 2 SHUTDOWN Bias Control Figure 39. Schematic Diagram of Typical Headphone Sense Application Table 3 details the logic for the mute function of the TPA4860. Table 3. Truth Table for Headphone Sense and Shutdown Functions INPUTS† OUTPUT HP-1 HP-2 SHUTDOWN HP-SENSE AMPLIFIER STATE Low Low Low Low Active Low High Low High Mute High Low Low High Mute High High Low High Mute X Shutdown X X High † Inputs should never be left unconnected. X = do not care shutdown mode The TPA4860 employs a shutdown mode of operation designed to reduce quiescent supply current, IDD(q), to the absolute minimum level during periods of nonuse for battery-power conservation. For example, during device sleep modes or when other audio-drive currents are used (i.e., headphone mode), the speaker drive is not required. The SHUTDOWN input terminal should be held low during normal operation when the amplifier is in use. Pulling SHUTDOWN high causes the outputs to mute and the amplifier to enter a low-current state, IDD < 1 µA. SHUTDOWN should never be left unconnected because amplifier operation would be unpredictable. using low-ESR capacitors Low-ESR capacitors are recommended throughout this applications section. A real capacitor can be modeled simply as a resistor in series with an ideal capacitor. The voltage drop across this resistor minimizes the beneficial effects of the capacitor in the circuit. The lower the equivalent value of this resistance the more the real capacitor behaves like an ideal capacitor. thermal considerations A prime consideration when designing an audio amplifier circuit is internal power dissipation in the device. The curve in Figure 40 provides an easy way to determine what output power can be expected out of the TPA4860 for a given system ambient temperature in designs using 5-V supplies. This curve assumes no forced airflow or additional heat sinking. 22 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 TPA4860 1-W MONO AUDIO POWER AMPLIFIER SLOS164A – SEPTEMBER 1996 – REVISED MARCH 2000 APPLICATION INFORMATION 160 VDD = 5 V TA – Free-Air Temperature – °C 140 RL = 16 Ω 120 100 80 RL = 8 Ω 60 40 RL = 4 Ω 20 0 0 0.25 0.5 0.75 1 1.25 1.50 Maximum Output Power – W Figure 40. Free-Air Temperature Versus Maximum Continuous Output Power 5-V versus 3.3-V operation The TPA4860 was designed for operation over a supply range of 2.7 V to 5.5 V. This data sheet provides full specifications for 5-V and 3.3-V operation, as these are considered to be the two most common standard voltages. There are no special considerations for 3.3-V versus 5-V operation as far as supply bypassing, gain setting, or stability. Supply current is slightly reduced from 3.5 mA (typical) to 2.5 mA (typical). The most important consideration is that of output power. Each amplifier in TPA4860 can produce a maximum voltage swing of VDD – 1 V. This means, for 3.3-V operation, clipping starts to occur when VO(PP) = 2.3 V as opposed to when VO(PP) = 4 V while operating at 5 V. The reduced voltage swing subsequently reduces maximum output power into an 8-Ω load to less than 0.33 W before distortion begins to become significant. Operation at 3.3-V supplies, as can be shown from the efficiency formula in equation 4, consumes approximately two-thirds the supply power for a given output-power level than operation from 5-V supplies. When the application demands less than 500 mW, 3.3-V operation should be strongly considered, especially in battery-powered applications. POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 23 TPA4860 1-W MONO AUDIO POWER AMPLIFIER SLOS164A – SEPTEMBER 1996 – REVISED MARCH 2000 MECHANICAL INFORMATION D (R-PDSO-G**) PLASTIC SMALL-OUTLINE PACKAGE 14 PINS SHOWN 0.050 (1,27) 0.020 (0,51) 0.014 (0,35) 14 0.010 (0,25) M 8 0.008 (0,20) NOM 0.244 (6,20) 0.228 (5,80) 0.157 (4,00) 0.150 (3,81) Gage Plane 0.010 (0,25) 1 7 0°– 8° A 0.044 (1,12) 0.016 (0,40) Seating Plane 0.069 (1,75) MAX 0.010 (0,25) 0.004 (0,10) PINS ** 0.004 (0,10) 8 14 16 A MAX 0.197 (5,00) 0.344 (8,75) 0.394 (10,00) A MIN 0.189 (4,80) 0.337 (8,55) 0.386 (9,80) DIM 4040047 / D 10/96 NOTES: A. B. C. D. 24 All linear dimensions are in inches (millimeters). This drawing is subject to change without notice. Body dimensions do not include mold flash or protrusion, not to exceed 0.006 (0,15). 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